without fail
1. If you do something without fail, you always do it:
I go to the gym every Monday and Wednesday, without fail.

2. used to tell someone that they must do something:
Be there at nine o'clock, without fail.

[TahlilGaran] Advanced Learner's Dictionary ▲

without fail
1.
if something happens without fail, it always happens.
Every Tuesday afternoon, without fail, Helga went to visit her father.

2.
something that you say in order to emphasize that something will be done or will happen.
'You will meet me at the airport, won't you?' 'Don't worry, I'll be there without fail.'

[TahlilGaran] English Idioms Dictionary ▲

without fail
absolutely, for certain
The postman came at noon everyday without fail.

[TahlilGaran] English Idioms Dictionary ▲

without fail
adv. phr. Without failing to do it or failing in the doing of it; certainly, surely.
Be here at 8 o'clock sharp, without fail.
Ben promised to return the bike at a certain time without fail.

[TahlilGaran] English Idioms Dictionary ▲